Preliminary investigation of Late Pleistocene fauna from Ryonggok Cave No. 1, Sangwon County,North Hwanghae Province,Democratic People's Republic of Korea

The investigation of a limestone cave on the Ryonggok-ri of Sangwon County, North Hwanghae Province, DPRK, has yielded many faunal remains including Late Pleistocene deer, brown bears and horses. Uranium series dating of fossil teeth yielded dates of ~72ka at the base of Layer 2 – the bone-bearing unit – and ~44ka at the top. The rich and diverse mammal remains of Ryonggok Cave No. 1 are indicative of warm and humid temperate conditions during the Late Pleistocene, and reflect the presence of both dense forests and open grassland. In addition, pollen and spores from the site include two families and 24 genera of trees, six families and a genus of grasses and herbs, and two families and six genera of ferns, corroborating the environments inferred from the faunal remains.     

The use of iron chemical analysis of podzols to date the Late Pleistocene–Holocene deglaciation history of the Central Italian Alps

Podzols that have developed on glacial and periglacial features provide the opportunity to reconstruct glacial evolution after the Last Glacial Maximum (LGM) using different soil indices. Analysing 17 soils classified as podzol, we used the crystallinity ratio of free iron oxides (CRF) on both the A and Bs horizons, and absolute ages for the same landforms containing the soil profile, to create dating curves. Two equations were generated: age = 4566.9 × ln (CRF) + 1760 (1), and age = 3907 × ln (CRF) + 3508.2 (2). The reliability of the curves was evaluated with the Fe_o/Fe_d ratio, and with the difference of ages calculated using both equations. Equation (2) is considered more reliable because the A horizon may be influenced by new pedogenesis on the pre-existing podzol, leading to the development of a new type of soil. By dating the soils, we reconstructed the glacial history of the three main upper branches of the LGM Adda Glacier in the Central Italian Alps, specifically the Stelvio Pass area (ST), Gavia Pass area (GV), and the Val Viola valley (VV). Seven glacial advances were identified at 16.7–14.7 ka (phase I), 12.3 ka (phase II), 11 ka (phase III), 10–9.7 ka (phase IV), 9 ka (phase V), 7.5 ka (phase VI) and 5.3 ka (phase VII). The first five phases are chronologically similar to the main Late Pleistocene–Early Holocene phases recorded in the Central European Alps. The last two Holocene phases, which are both longer in duration than the Little Ice Age, are recorded in ST and GV. Interestingly, these phases generally are not recorded in the rest of the Central European Alps, where the late Holocene glaciers were smaller than their present size.     

The Campo Felice late Pleistocene Glaciation (Apennines,central Italy)

Study of the glacial deposits and lacustrine sediments of Campo Felice (Apennines, central Italy) has enabled the glacial phases of the last 40 ka to be dated more precisely, and has demonstrated that the maximum glacial advance did not occur in correspondence with the last global glacial maximum and with the coldest and most arid phase suggested by the pollen, but in a period dated between about 33 and 27 ka, characterized by a less extreme climate. Furthermore, a glacial expansion took place also in the period prior to 35 ka. Correlation with the Alpine glacial variations has shown that the Apennine last glacial maximum occurred before that of the southern slope of the Alps. Copyright © 2012 John Wiley & Sons, Ltd.     

Rock glaciers in the northern Japanese Alps: palaeoenvironmental implications since the Late Glacial

In order to determine the palaeoclimatic and palaeo‐permafrost conditions in the northern Japanese Alps in central Japan, the ages of rock glaciers were investigated by relative age dating techniques such as weathering‐rind thickness and Schmidt hammer measurements. The results of the relative age dating suggest that the formation of the investigated rock glaciers may have started during the early phase of the Late Glacial or around the onset of the Holocene. The lower limit of current discontinuous permafrost in the northern Japanese Alps, which is indicated by the terminus of the lowest active/inactive rock glacier, lies at 2530 m a.s.l., while that of discontinuous permafrost during the Late Glacial or early phase of the Holocene, which is indicated by the terminus of the lowest relict rock glacier, lies at 2220 m a.s.l. Therefore, the lower limit of discontinuous permafrost during these periods would have been at least about 300 m lower than that of the current discontinuous permafrost. Climatic and geomorphological conditions during the Late Glacial led to a change in the environment from a glacial environment to a periglacial (permafrost) environment in the current alpine zone of the northern Japanese Alps. A large number of cirques were deglaciated and several of them were occupied by active rock glaciers around the onset of the Holocene. Copyright © 2005 John Wiley & Sons, Ltd.     

The C20 highly branched isoprenoid biomarker – A new diatom-sourced proxy for summer trophic conditions?

The exact biological source of the C₂₀ highly branched isoprenoid (HBI) present in sediments from aquatic systems is unclear. We therefore examined the relationship between the distribution of fossil diatoms and the concentration of the C₂₀ HBI in a Late Glacial sedimentary record from the Hässeldala Port paleolake in southern Sweden. Using Bayesian multiple linear regression analysis, we show that its concentration is linked primarily to the production of the diatom taxon Gomphonema acuminatum, which accounts for the largest proportion of the temporal variability in the biomarker. By analogy with modern observations, we argue that an increasing amount of G. acuminatum biomass in our sedimentary record reflects increasing oligotrophy in the paleolake during the summer growing season, especially at times defined by subdued hydrologic flow. Our conclusions are corroborated by the δ¹³C composition of the C₂₀ HBI biomarker, which points to a negative photosynthetic fractionation between atmospheric CO₂ and the pool of dissolved inorganic carbon during diatom bloom, a distinct phenomenon at times of inhibited hydrological flow. Accordingly, we suggest that the C₂₀ HBI biomarker can be effectively used to reconstruct the trophic state of the paleolake at Hässeldala Port, while its stable isotope composition can provide physicochemical information about the lake conditions during the dry summer season.Moreover, we note that the major hydrological shifts recorded in the G. acuminatum-C₂₀ HBI stratigraphy do not coincide with the pollen zone boundaries. We thus infer that aquatic and terrestrial environmental responses to climate change are substantially decoupled through the hydrological system, which highlights the necessity for multi-proxy investigations to decipher past climate events.     

Florida Bay: Modern analogue for Lofer cyclothems?

Lofer cyclothems of the Alpine Upper Triassic have many features in common with Holocene sediments of Florida Bay. The modal ‘complete’ Lofer cycle is essentially symmetrical, having a deepening and shoaling phase, as does the cycle-in-progress in Florida Bay. Lateral discontinuity and thickness variations within members of the Lofer cyclothems indicate syn-depositional relief, possibly in the form of mud banks, the signature feature of Florida Bay sedimentation. Spatial and temporal dimensions, although poorly constrained, appear comparable. Analogous depositional textures, biota and sedimentary structures, while not unique to either environment, strengthen the inferences that can be made about the Triassic depositional environment and regarding future evolution of the modern environment. The striking similarities between the Holocene icehouse sediments and the Late Triassic greenhouse deposits suggest that sedimentation patterns at the scale of individual cycles or parasequences may be largely independent of the global climate regime.     

甘肃北山红石山地区晚石炭世英云闪长岩锆石U- Pb年龄、地球化学特征及构造意义

本文以出露于红石山—百合山蛇绿混杂岩带南侧的英云闪长岩体为研究对象,通过野外地质调查和岩石学、地球化学、锆石LA- ICP- MS U- Pb年代学研究,探讨其成因、构造环境及红石山洋俯冲消亡过程。岩石地球化学研究表明,红石山南英云闪长岩体富硅（SiO2=63. 95%～66. 22%）、高铝（Al2O3=15. 31%～16. 61%）、富钠（Na2O=3. 73%～4. 33%）、低钾（K2O=1. 00%～1. 85%）,相对高锶（Sr=246. 0×10-6～417. 0×10-6）、低钇（Y=8. 83×10-6～11. 80×10-6）,富集Rb、Sr等大离子亲石元素和LREE,亏损Nb、Ta、Ti、P等高场强元素,HREE相对亏损,无明显Eu异常。岩石学和岩石地球化学特征表明,为俯冲洋壳脱水熔融的产物。锆石LA- ICP- MS U- Pb测年表明,红石山南英云闪长岩体的形成年龄为306. 9～309. 9 Ma,表明该岩体侵位于晚石炭世,反映了红石山—百合山缝合带晚石炭世大洋俯冲带岩浆作用事件,进一步约束了红石山洋俯冲时限。结合红石山—百合山缝合带石炭纪蛇绿岩、石炭纪—二叠纪岛弧型岩浆岩和早二叠世末期（275 Ma）的辉长岩和花岗岩侵位及早—中二叠世双堡塘组下部的角度不整合均反映了红石山洋盆的闭合过程（辛后田等,2020）,表明红石山洋盆在晚石炭世并未关闭,而是处于大洋俯冲消减和陆壳增生过程中。     

大兴安岭北段富克山岩浆弧的组成:对蒙古—鄂霍茨克洋南向俯冲的制约

富克山岩浆弧呈北东向分布于大兴安岭北段富克山—古莲河一带,其物质组成、形成时代及其空间展布规律对于研究蒙古—鄂霍茨克洋晚三叠世地质构造演化具有重要意义。本文对其内的辉长岩、闪长岩、花岗闪长岩进行了岩石学、地球化学及锆石U-Pb定年分析研究,探讨大兴安岭北段晚三叠世时期的构造背景。LA-ICP-MS锆石U-Pb定年获得辉长岩、花岗闪长岩的结晶年龄分别为(205.7±2.2) Ma、(203.2±2.5) Ma,反映了晚三叠世的构造岩浆事件。岩石学和地球化学研究表明,辉长岩、闪长岩具有富钠、高铝、高钙、高镁、高Mg^#值、低钛等特征,属于拉斑系列与钙碱性过渡系列岩石,无明显的Eu负异常,相对富集LILE和LREE,亏损HFSE。花岗闪长岩具有高硅、富钠、高铝、低镁等特征,属于钙碱性系列岩石,高Sr,低Y、Yb,无明显的Eu负异常,显示了O型埃达克质岩石的地球化学特征。富克山岩浆弧的空间展布,具有由北向南的分布规律,指示了蒙古—鄂霍茨克洋具有往南的俯冲极性。     

鄂尔多斯盆地西南部晚三叠世辉绿岩年代学、地球化学及其构造意义

鄂尔多斯盆地西南部中奥陶统马家沟组灰岩内部发育多条辉绿岩脉。辉绿岩富集高场强元素(HFSE)Nb、Ta、Ti、Zr、Hf等,具有板内拉斑玄武岩的地球化学特征,其地球化学数据显示原始岩浆经历过比较强烈的结晶分异演化。对辉绿岩的锆石进行U-Pb LA-ICP-MS测年获得的²⁰⁶Pb/²³⁸U年龄为750~195 Ma。根据峰值年龄并结合区域地质资料,本文把辉绿岩的形成年龄确定为224 Ma(晚三叠世)。辉绿岩反映鄂尔多斯盆地西南部在晚三叠世处于类似大陆裂谷的伸展构造环境,晚三叠世西邻陇山地区发生的强烈碰撞后伸展作用也可能有助于进一步强化鄂尔多斯盆地西南部的伸展构造环境。当时该地区岩石圈的稳定性相对较弱,为该地区后续的早侏罗世和早白垩世岩浆活动提供了物质基础。晚三叠世及后期的岩浆活动提高了鄂尔多斯盆地西南部的地温梯度并加快了该地区烃源岩的热演化进程,可能对该地区的油气成藏条件造成潜在影响。     

中国北方中生代逆冲推覆构造研究进展

推覆构造是陆内构造变形中地壳缩短的重要方式之一, 是记录盆山结合带-造山带形成演化过程的重要载体。中国北方位于中亚造山带南部及周缘地区, 分布了多个逆冲推覆构造带。本文通过对这些推覆构造相关的几何学、运动学和年代学等资料的综合收集分析, 梳理了中国北方众多中生代逆冲推覆构造的时空展布特征、形成时代及形成机制等。在空间展布上, 这些推覆构造沿中国北方近东西向展布, 推覆距离几十~几百公里不等, 属于浅层次脆性变形。在形成时代上, 这些推覆构造的时代可以和燕山运动主挤压变形期相对应, 分为早(170~160 Ma)和晚(150~135 Ma)两期。在动力学机制上, 本文将推覆体可分为东西两段, 西段主体的逆冲方向为北东—南西向, 可能受控于鄂霍次克洋闭合和班公湖—怒江缝合带闭合的综合影响; 东段主体逆冲方向为北西—南东向, 可能主要受控于鄂霍茨克洋的闭合与古太平洋板块俯冲的远程应力影响。